Abstract
We show that readily available α‐amidoaldehydes are effective substrates for intermolecular Rh‐catalyzed alkyne hydroacylation reactions. The catalyst [Rh(dppe)(C6H5F)][BArF 4] provides good reactivity, and allows a broad range of aldehydes and alkynes to be used as substrates, delivering α‐amidoketone products. High yields and high levels of regioselectivity are achieved. The use of α‐amidoaldehydes as substrates establishes that 1,4‐dicarbonyl motifs can be used as controlling groups in Rh‐catalyzed hydroacylation reactions.
Highlights
We show that readily available a-amidoaldehydes are effective substrates for intermolecular Rh-catalyzed alkyne hydroacylation reactions
Transition-metal-catalyzed hydroacylation has emerged as a powerful and robust method to prepare ketones.[1a]. Hydroacylation involves the addition of an aldehyde across the carbon– carbon p-bond of an alkene or alkyne, to form a ketone or an enone, respectively (Scheme 1 a).[1]
Rhodium(I) complexes are the most commonly used catalysts, and the success of these reactions is often related to the stability of key metal-acyl hydride intermediates, which are formed after oxidative addition of the aldehyde to the rhodium complex.[2]
Summary
We show that readily available a-amidoaldehydes are effective substrates for intermolecular Rh-catalyzed alkyne hydroacylation reactions. The reaction uses readily available a-amidoaldehydes as substrates, and demonstrates that, in the context of Rh-catalyzed hydroacylation, the presumed 6-membered metallocycles accessed from 1,4-dicarbonyl compounds, are effective stabilizing motifs. Full conversion (80 % isolated yield) and increased regioselectivity (7:1 to 10:1) was achieved using 5 mol % catalyst (entry 8), and importantly, the reaction could be performed at 40 8C in CH2Cl2, compared to 80 8C needed in the original reaction.
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